This invention relates to a method for making a semiconductor structure and more particularly to a method of making isolated integrated circuitry.
At the present time, the conventional integrated circuitry is isolated by the use of p-n junctions. It has been found that p-n junctions have a number of disadvantages. One is that there is an appreciable leakage associated with such junctions particularly at elevated temperatures. Also, there is a very high capacitance per unit area associated with such junctions. Furthermore, a p-n junction has a disadvantage in that it has a high resistance in one direction only. As a result, in most integrated circuitry, the speed and performance are limited primarily not by the active elements but by the isolating p-n junctions. There is, therefore, a need for a new and improved structure and method which can be utilized for isolating active and passive elements in integrated circuitry.
In general, it is an object of the present invention to provide a semiconductor structure and a method for fabricating the same whereby greatly improved isolation is obtained between the passive and active elements of the integrated circuitry.
Another object of the invention is to provide a semiconductor structure of the above character in which isolated islands of semiconductor material are provided in which active and passive elements can be formed.
Another object of the invetion is to provide a semiconductor structure of the above character in which insulating material electrically insulates the islands for a support structure.
Another object of the invention is to provide a semiconductor structure of the above character in which the support structure can have a very high resistance.
Another object of the invention is to provide a semiconductor structure of the above character in which active and passive elements can be formed in the isolated islands by substantially conventional techniques.
Another object of the invention is to provide a semiconductor structure of the above character in which the islands have a uniform depth with surfaces lying in a common plane.
Another object of the invention is to provide a semiconductor structure of the above character in which epitaxial techniques can be utilized in the formation of the support structure and of the active and passive elements in the isolated islands.
Another object of the invention is to provide a semiconductor structure of the above character in which substantially conventional materials can be utilized.
Another object of the invention is to provide a method of the above character which can be performed utilizing substantially conventional apparatus.
Another object of the invention is to provide a method of the above character which can be rapidly and easily performed.
Additional objects and features of the invention will appear from the following description in which the preferred embodiment of the invention is set forth in detail in conjunction with the accompanying drawings.